Storage aggregate restoration

ABSTRACT

One or more techniques and/or systems are provided for controlling restoration of a storage aggregate. For example, a local storage device, located at a first storage site, and a remote storage device, located at a second storage site, may be assigned to a first storage aggregate. Responsive to a disaster of the first storage site, a gate may be created for the local storage device. The gate may block automated reconstruction and/or automated synchronization that may otherwise occur with respect to the local storage device. Until the local storage device is restored, the remote storage device may be used to service I/O requests that were otherwise directed to the local storage device. Responsive to receiving a user restoration command, the gate may be removed from the local storage device. Synchronization between the local storage device and the remote storage device may then be facilitated.

RELATED APPLICATION

This application claims priority to and is a continuation of U.S. patentapplication Ser. No. 15/468,896, filed on Mar. 24, 2017 and titled“STORAGE AGGREGATE RESTORATION,” which claims priority to and is acontinuation of U.S. Pat. No. 9,619,352, filed on Mar. 20, 2014 andtitled “STORAGE AGGREGATE RESTORATION,” which are incorporated herein byreference.

BACKGROUND

A network storage environment may comprise one or more storagecontrollers configured to provide client devices with access to datastored on storage devices accessible from the respective storagecontrollers.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a component block diagram illustrating an example clusterednetwork in accordance with one or more of the provisions set forthherein.

FIG. 2 is a component block diagram illustrating an example data storagesystem in accordance with one or more of the provisions set forthherein.

FIG. 3 is a flow chart illustrating an exemplary method of controllingrestoration of a storage aggregate.

FIG. 4A is an example of a first storage site comprising a storagecontroller (A1) and a storage controller (A2).

FIG. 4B is an example of identifying a disaster of a first storage site.

FIG. 4C is an example of a storage controller (B1) and/or a storagecontroller (B2) taking ownership of a first remote storage device (A)and/or a second remote storage device (A).

FIG. 4D is an example of restoring a first local storage device (A)and/or a second local storage device (A).

FIG. 4E is an example of a gate component concurrently removing a firstgate and a second gate based upon a user restoration command.

FIG. 4F is an example of restoring a storage controller (A1) and astorage controller (A2) at a first storage site.

FIG. 4G is an example of reassigning ownership of one or more storagedevices.

FIG. 5 is an example of a computer readable medium in accordance withone or more of the provisions set forth herein.

DETAILED DESCRIPTION

Some examples of the claimed subject matter are now described withreference to the drawings, where like reference numerals are generallyused to refer to like elements throughout. In the following description,for purposes of explanation, numerous specific details are set forth inorder to provide an understanding of the claimed subject matter. It maybe evident, however, that the claimed subject matter may be practicedwithout these specific details. Nothing in this detailed description isadmitted as prior art.

One or more systems and/or techniques for controlling restoration of astorage aggregate are provided. Within a network storage environment, afirst set of storage controllers are located at a first or local storagesite (e.g., a first location such as a first city) and a second set ofstorage controllers are located at a second or remote storage site(e.g., a second location such as a second city). The first set ofstorage controllers may manage a first storage aggregate (e.g., alogical grouping of storage devices that may be assigned to or owned bythe first set of storage controllers) and the second set of storagecontrollers may manage a second storage aggregate (e.g., a logicalgrouping of storage devices that may be assigned to or owned by thesecond set of storage controllers). A local storage device associatedwith the first storage aggregate, and thus managed by the first set ofstorage controllers at the first storage site, may be located at thefirst storage site and a remote storage device associated with the firststorage aggregate, and thus also managed by the first set of storagecontrollers at the first storage site, may be located at the secondstorage site. Data may be mirrored from the local storage device to theremote storage device for disaster recovery and/or switchover operation.If a disaster associated with the first storage site occurs, then thesecond set of storage controllers at the second storage site may takeover the remote storage device for switchover operation so that thesecond set of storage controllers may provide data access to the firststorage aggregate utilizing the data mirrored to the remote storagedevice from the local storage device. In this way, disaster recoveryand/or continued access to data may be provided. When the disaster atthe first storage site is resolved, the local storage device is restoredat the first storage site. As provided herein, a gate may be created forthe local storage device during switchover of the remote storage deviceto the second set of storage controllers when the first storage site hasa disaster and/or during restoration of the local storage device at thefirst storage site when the disaster at the first storage site isresolved.

In an example of a gate, the gate may block automated reconstruction ofthe local storage device and/or other local storage devices, which maymitigate unnecessary reconstruction of local storages devices duringrestoration of the first storage site. For example, a first localstorage device may be recognized as being paired with a second localstorage device. During restoration of the first storage site, the firstlocal storage device may come online before the second local storagedevice (e.g., an administrator may power on the first local storagedevice, and may then proceed to power on the second local storagedevice). Without the gate, automatic reconstruction of the second localstorage device may occur (e.g., based upon a determination that thefirst local storage device is online and that the second local storagedevice is not online), which may be unnecessary because the second localstorage device may come online shortly after the first local storagedevice (e.g., once the administrator powers on the second local storagedevice). In this way, gates are created for local storage devices sothat the local storage devices are concurrently brought online (e.g.,based upon a user restoration command issued by the administrator afterthe administrator is finished powering on the local storage devices).

In another example of a gate, the gate may block automatedsynchronization of the local storage device using the remote storagedevice. Without the gate, automated synchronization may overwrite thelocal storage device with data from the remote storage device, however,the data within the local storage device may be preferred over the datafrom the remote storage device (e.g., even though the local storagedevice may have been offline for a while). In this way, the gate mayblock the automated synchronization until a user restoration commandcomprising a user designation of a synchronization template is received,for example. For example, once the first storage site is restored,storage device synchronization may be performed based upon the userdesignation of either the local storage device or the remote storagedevice as the synchronization template (e.g., the administrator mayspecify whether local storage devices are to be synchronized based uponremote storage devices or whether remote storage devices are to besynchronized based upon local storage devices).

To provide context for controlling restoration of a storage aggregate,FIG. 1 illustrates an embodiment of a clustered network environment or anetwork storage environment 100. It may be appreciated, however, thatthe techniques, etc. described herein may be implemented within theclustered network environment 100, a non-cluster network environment,and/or a variety of other computing environments, such as a desktopcomputing environment. That is, the instant disclosure, including thescope of the appended claims, is not meant to be limited to the examplesprovided herein. It will be appreciated that where the same or similarcomponents, elements, features, items, modules, etc. are illustrated inlater figures but were previously discussed with regard to priorfigures, that a similar (e.g., redundant) discussion of the same may beomitted when describing the subsequent figures (e.g., for purposes ofsimplicity and ease of understanding).

FIG. 1 is a block diagram illustrating an example clustered networkenvironment 100 that may implement at least some embodiments of thetechniques and/or systems described herein. The example environment 100comprises data storage systems or storage sites 102 and 104 that arecoupled over a cluster fabric 106, such as a computing network embodiedas a private Infiniband or Fibre Channel (FC) network facilitatingcommunication between the storage systems 102 and 104 (and one or moremodules, component, etc. therein, such as, nodes 116 and 118, forexample). It will be appreciated that while two data storage systems 102and 104 and two nodes 116 and 118 are illustrated in FIG. 1, that anysuitable number of such components is contemplated. In an example, nodes116, 118 comprise storage controllers (e.g., node 116 may comprise aprimary or local storage controller and node 118 may comprise asecondary or remote storage controller) that provide client devices,such as host devices 108, 110, with access to data stored within datastorage devices 128, 130. Similarly, unless specifically providedotherwise herein, the same is true for other modules, elements,features, items, etc. referenced herein and/or illustrated in theaccompanying drawings. That is, a particular number of components,modules, elements, features, items, etc. disclosed herein is not meantto be interpreted in a limiting manner.

It will be further appreciated that clustered networks are not limitedto any particular geographic areas and can be clustered locally and/orremotely. Thus, in one embodiment a clustered network can be distributedover a plurality of storage systems and/or nodes located in a pluralityof geographic locations; while in another embodiment a clustered networkcan include data storage systems (e.g., 102, 104) residing in a samegeographic location (e.g., in a single onsite rack of data storagedevices).

In the illustrated example, one or more host devices 108, 110 which maycomprise, for example, client devices, personal computers (PCs),computing devices used for storage (e.g., storage servers), and othercomputers or peripheral devices (e.g., printers), are coupled to therespective data storage systems 102, 104 by storage network connections112, 114. Network connection may comprise a local area network (LAN) orwide area network (WAN), for example, that utilizes Network AttachedStorage (NAS) protocols, such as a Common Internet File System (CIFS)protocol or a Network File System (NFS) protocol to exchange datapackets. Illustratively, the host devices 108, 110 may begeneral-purpose computers running applications, and may interact withthe data storage systems 102, 104 using a client/server model forexchange of information. That is, the host device may request data fromthe data storage system (e.g., data on a storage device managed by anetwork storage control configured to process I/O commands issued by thehost device for the storage device), and the data storage system mayreturn results of the request to the host device via one or more networkconnections 112, 114.

The nodes 116, 118 on clustered data storage systems 102, 104 cancomprise network or host nodes that are interconnected as a cluster toprovide data storage and management services, such as to an enterprisehaving remote locations, for example. Such a node in a data storage andmanagement network cluster environment 100 can be a device attached tothe network as a connection point, redistribution point or communicationendpoint, for example. A node may be capable of sending, receiving,and/or forwarding information over a network communications channel, andcould comprise any device that meets any or all of these criteria. Oneexample of a node may be a data storage and management server attachedto a network, where the server can comprise a general purpose computeror a computing device particularly configured to operate as a server ina data storage and management system.

In an example, a first cluster of nodes such as the nodes 116, 118(e.g., a first set of storage controllers configured to provide accessto a first storage aggregate comprising a first logical grouping of oneor more storage devices) may be located on a first storage site. Asecond cluster of nodes, not illustrated, may be located at a secondstorage site (e.g., a second set of storage controllers configured toprovide access to a second storage aggregate comprising a second logicalgrouping of one or more storage devices). The first cluster of nodes andthe second cluster of nodes may be configured according to a disasterrecovery configuration where a surviving cluster of nodes providesswitchover access to storage devices of a disaster cluster of nodes inthe event a disaster occurs at a disaster storage site comprising thedisaster cluster of nodes (e.g., the first cluster of nodes providesclient devices with switchover data access to storage devices of thesecond storage aggregate in the event a disaster occurs at the secondstorage site).

As illustrated in the exemplary environment 100, nodes 116, 118 cancomprise various functional components that coordinate to providedistributed storage architecture for the cluster. For example, the nodescan comprise a network module 120, 122 a Disk Module 124, 126. Networkmodules 120, 122 can be configured to allow the nodes 116, 118 (e.g.,network storage controllers) to connect with host devices 108, 110 overthe network connections 112, 114, for example, allowing the host devices108, 110 to access data stored in the distributed storage system.Further, the network modules 120, 122 can provide connections with oneor more other components through the cluster fabric 106. For example, inFIG. 1, a first network module 120 of first node 116 can access a seconddata storage device 130 by sending a request through a second DiskModule 126 of a second node 118.

Disk Modules 124, 126 can be configured to connect one or more datastorage devices 128, 130, such as disks or arrays of disks, flashmemory, or some other form of data storage, to the nodes 116, 118. Thenodes 116, 118 can be interconnected by the cluster fabric 106, forexample, allowing respective nodes in the cluster to access data on datastorage devices 128, 130 connected to different nodes in the cluster.Often, Disk Modules 124, 126 communicate with the data storage devices128, 130 according to a storage area network (SAN) protocol, such asSmall Computer System Interface (SCSI) or Fiber Channel Protocol (FCP),for example. Thus, as seen from an operating system on a node 116, 118,the data storage devices 128, 130 can appear as locally attached to theoperating system. In this manner, different nodes 116, 118, etc. mayaccess data blocks through the operating system, rather than expresslyrequesting abstract files.

It should be appreciated that, while the example embodiment 100illustrates an equal number of N and D modules, other embodiments maycomprise a differing number of these modules. For example, there may bea plurality of N and/or D modules interconnected in a cluster that doesnot have a one-to-one correspondence between the N and D modules. Thatis, different nodes can have a different number of N and D modules, andthe same node can have a different number of N modules than D modules.

Further, a host device 108, 110 can be networked with the nodes 116, 118in the cluster, over the networking connections 112, 114. As an example,respective host devices 108, 110 that are networked to a cluster mayrequest services (e.g., exchanging of information in the form of datapackets) of a node 116, 118 in the cluster, and the node 116, 118 canreturn results of the requested services to the host devices 108, 110.In one embodiment, the host devices 108, 110 can exchange informationwith the network modules 120, 122 residing in the nodes (e.g., networkhosts) 116, 118 in the data storage systems 102, 104.

In one embodiment, the data storage devices 128, 130 comprise volumes132, which is an implementation of storage of information onto diskdrives or disk arrays or other storage (e.g., flash) as a file-systemfor data, for example. Volumes can span a portion of a disk, acollection of disks, or portions of disks, for example, and typicallydefine an overall logical arrangement of file storage on disk space inthe storage system. In one embodiment a volume can comprise stored dataas one or more files that reside in a hierarchical directory structurewithin the volume.

Volumes are typically configured in formats that may be associated withparticular storage systems, and respective volume formats typicallycomprise features that provide functionality to the volumes, such asproviding an ability for volumes to form clusters. For example, where afirst storage system may utilize a first format for their volumes, asecond storage system may utilize a second format for their volumes.

In the example environment 100, the host devices 108, 110 can utilizethe data storage systems 102, 104 to store and retrieve data from thevolumes 132. In this embodiment, for example, the host device 108 cansend data packets to the Network Module 120 in the node 116 within datastorage system 102. The node 116 can forward the data to the datastorage device 128 using the Disk Module 124, where the data storagedevice 128 comprises volume 132A. In this way, in this example, the hostdevice can access the storage volume 132A, to store and/or retrievedata, using the data storage system 102 connected by the networkconnection 112. Further, in this embodiment, the host device 110 canexchange data with the Network Module 122 in the host 118 within thedata storage system 104 (e.g., which may be remote from the data storagesystem 102). The host 118 can forward the data to the data storagedevice 130 using the Disk Module 126, thereby accessing volume 1328associated with the data storage device 130.

It may be appreciated that storage aggregate restoration may beimplemented within the clustered network environment 100. For example, agate component may be implemented for the data storage device 128 and/orthe data storage device 130. The gate component may be configured tocreate a gate for the data storage device 128 and/or the data storagedevice 130. The gate may block automated reconstruction of a datastorage device and/or may block automated synchronization of a storagedevice. In this way, data storage devices may be concurrently broughtonline during disaster recovery (e.g., recovery of the data storagesystem or storage site 102 and/or the data storage system or storagesite 104) and a user, such as an administrator, may selectively choosewhat data storage devices to use as synchronization templates.

FIG. 2 is an illustrative example of a data storage system or storagesite 200 (e.g., 102, 104 in FIG. 1), providing further detail of anembodiment of components that may implement one or more of thetechniques and/or systems described herein. The example data storagesystem 200 comprises a node 202 (e.g., host nodes 116, 118 in FIG. 1),and a data storage device 234 (e.g., data storage devices 128, 130 inFIG. 1). The node 202 may be a general purpose computer, for example, orsome other computing device particularly configured to operate as astorage server. A host device 205 (e.g., 108, 110 in FIG. 1) can beconnected to the node 202 over a network 216, for example, to providesaccess to files and/or other data stored on the data storage device 234.In an example, the node 202 comprises a storage controller that providesclient devices, such as the host device 205, with access to data storedwithin data storage device 234.

The data storage device 234 can comprise mass storage devices, such asdisks 224, 226, 228 of a disk array 218, 220, 222. It will beappreciated that the techniques and systems, described herein, are notlimited by the example embodiment. For example, disks 224, 226, 228 maycomprise any type of mass storage devices, including but not limited tomagnetic disk drives, flash memory, and any other similar media adaptedto store information, including, for example, data (D) and/or parity (P)information.

The node 202 comprises one or more processors 204, a memory 206, anetwork adapter 210, a cluster access adapter 212, and a storage adapter214 interconnected by a system bus 242. The storage system 200 alsoincludes an operating system 208 installed in the memory 206 of the node202 that can, for example, implement a Redundant Array of Independent(or Inexpensive) Disks (RAID) optimization technique to optimize areconstruction process of data of a failed disk in an array.

The operating system 208 can also manage communications for the datastorage system, and communications between other data storage systemsthat may be in a clustered network, such as attached to a cluster fabric215 (e.g., 106 in FIG. 1). Thus, the node 202, such as a network storagecontroller, can respond to host device requests to manage data on thedata storage device 234 (e.g., or additional clustered devices) inaccordance with these host device requests. The operating system 208 canoften establish one or more file systems on the data storage system 200,where a file system can include software code and data structures thatimplement a persistent hierarchical namespace of files and directories,for example. As an example, when a new data storage device (not shown)is added to a clustered network system, the operating system 208 isinformed where, in an existing directory tree, new files associated withthe new data storage device are to be stored. This is often referred toas “mounting” a file system.

In the example data storage system 200, memory 206 can include storagelocations that are addressable by the processors 204 and adapters 210,212, 214 for storing related software program code and data structures.The processors 204 and adapters 210, 212, 214 may, for example, includeprocessing elements and/or logic circuitry configured to execute thesoftware code and manipulate the data structures. The operating system208, portions of which are typically resident in the memory 206 andexecuted by the processing elements, functionally organizes the storagesystem by, among other things, invoking storage operations in support ofa file service implemented by the storage system. It will be apparent tothose skilled in the art that other processing and memory mechanisms,including various computer readable media, may be used for storingand/or executing program instructions pertaining to the techniquesdescribed herein. For example, the operating system can also utilize oneor more control files (not shown) to aid in the provisioning of virtualmachines.

The network adapter 210 includes the mechanical, electrical andsignaling circuitry needed to connect the data storage system 200 to ahost device 205 over a computer network 216, which may comprise, amongother things, a point-to-point connection or a shared medium, such as alocal area network. The host device 205 (e.g., 108, 110 of FIG. 1) maybe a general-purpose computer configured to execute applications. Asdescribed above, the host device 205 may interact with the data storagesystem 200 in accordance with a client/host model of informationdelivery.

The storage adapter 214 cooperates with the operating system 208executing on the node 202 to access information requested by the hostdevice 205 (e.g., access data on a storage device managed by a networkstorage controller). The information may be stored on any type ofattached array of writeable media such as magnetic disk drives, flashmemory, and/or any other similar media adapted to store information. Inthe example data storage system 200, the information can be stored indata blocks on the disks 224, 226, 228. The storage adapter 214 caninclude input/output (I/O) interface circuitry that couples to the disksover an I/O interconnect arrangement, such as a storage area network(SAN) protocol (e.g., Small Computer System Interface (SCSI), iSCSI,hyperSCSI, Fiber Channel Protocol (FCP)). The information is retrievedby the storage adapter 214 and, if necessary, processed by the one ormore processors 204 (or the storage adapter 214 itself) prior to beingforwarded over the system bus 242 to the network adapter 210 (and/or thecluster access adapter 212 if sending to another node in the cluster)where the information is formatted into a data packet and returned tothe host device 205 over the network connection 216 (and/or returned toanother node attached to the cluster over the cluster fabric 215).

In one embodiment, storage of information on arrays 218, 220, 222 can beimplemented as one or more storage “volumes” 230, 232 that are comprisedof a cluster of disks 224, 226, 228 defining an overall logicalarrangement of disk space. The disks 224, 226, 228 that comprise one ormore volumes are typically organized as one or more groups of RAIDs. Asan example, volume 230 comprises an aggregate of disk arrays 218 and220, which comprise the cluster of disks 224 and 226.

In one embodiment, to facilitate access to disks 224, 226, 228, theoperating system 208 may implement a file system (e.g., write anywherefile system) that logically organizes the information as a hierarchicalstructure of directories and files on the disks. In this embodiment,respective files may be implemented as a set of disk blocks configuredto store information, whereas directories may be implemented asspecially formatted files in which information about other files anddirectories are stored.

Whatever the underlying physical configuration within this data storagesystem 200, data can be stored as files within physical and/or virtualvolumes, which can be associated with respective volume identifiers,such as file system identifiers (FSIDs), which can be 32-bits in lengthin one example.

A physical volume corresponds to at least a portion of physical storagedevices whose address, addressable space, location, etc. doesn't change,such as at least some of one or more data storage devices 234 (e.g., aRedundant Array of Independent (or Inexpensive) Disks (RAID system)).Typically the location of the physical volume doesn't change in that the(range of) address(es) used to access it generally remains constant.

A virtual volume, in contrast, is stored over an aggregate of disparateportions of different physical storage devices. The virtual volume maybe a collection of different available portions of different physicalstorage device locations, such as some available space from each of thedisks 224, 226, and/or 228. It will be appreciated that since a virtualvolume is not “tied” to any one particular storage device, a virtualvolume can be said to include a layer of abstraction or virtualization,which allows it to be resized and/or flexible in some regards.

Further, a virtual volume can include one or more logical unit numbers(LUNs) 238, directories 236, qtrees 235, and files 240. Among otherthings, these features, but more particularly LUNS, allow the disparatememory locations within which data is stored to be identified, forexample, and grouped as data storage unit. As such, the LUNs 238 may becharacterized as constituting a virtual disk or drive upon which datawithin the virtual volume is stored within the aggregate. For example,LUNs are often referred to as virtual drives, such that they emulate ahard drive from a general purpose computer, while they actually comprisedata blocks stored in various parts of a volume.

In one embodiment, one or more data storage devices 234 can have one ormore physical ports, wherein each physical port can be assigned a targetaddress (e.g., SCSI target address). To represent respective volumesstored on a data storage device, a target address on the data storagedevice can be used to identify one or more LUNs 238. Thus, for example,when the node 202 connects to a volume 230, 232 through the storageadapter 214, a connection between the node 202 and the one or more LUNs238 underlying the volume is created.

In one embodiment, respective target addresses can identify multipleLUNs, such that a target address can represent multiple volumes. The I/Ointerface, which can be implemented as circuitry and/or software in thestorage adapter 214 or as executable code residing in memory 206 andexecuted by the processors 204, for example, can connect to volume 230by using one or more addresses that identify the LUNs 238.

It may be appreciated that storage aggregate restoration may beimplemented for the data storage system or storage site 200. Forexample, a gate component may be implemented for the data storage device234. The gate component may be configured to create a gate for the datastorage device 234. The gate may block automated reconstruction of thedata storage device 234 and/or may block automated synchronization ofthe data storage device 234. In this way, the data storage device 234may be concurrently brought online with other data storage devicesduring disaster recovery (e.g., recovery of the data storage system orstorage site 200) and a user, such as an administrator, may selectivelychoose what data storage devices to use as synchronization templates.

One embodiment of controlling restoration of a storage aggregate isillustrated by an exemplary method 300 of FIG. 3. At 302, the methodstarts. At 304, a local storage device located at a first storage sitemay be identified. The local storage device may be assigned to a firststorage aggregate. In an example, one or more storage controllers at thefirst storage site (e.g., a first cluster), such as a first storagecontroller and a second storage controller, may provide I/O access todata stored within the first storage aggregate. In an example, one ormore additional local storage devices may be located at the firststorage site and are assigned to the first storage aggregate, such as asecond local storage device (e.g., having a raid configuration or otherbackup configuration with respect to the local storage device).

At 306, a remote storage device located at a second storage site may beidentified. The remote storage device is assigned to the first storageaggregate. The remote storage device and the local storage device may beconfigured according to a data pairing configuration (e.g., a highavailability configuration) for the first storage aggregate (e.g., datamay be mirrored from the local storage device to the remote storagedevice so that the remote storage device may be used for switchoveroperation in place of the local storage device in the event a failure ofthe local storage device occurs). In an example, one or more storagecontrollers at the second storage site (e.g., a second cluster), such asa third storage controller and a fourth storage controller, may provideI/O access to data stored within one or more storage devices assigned toa second storage aggregate. Storage controllers at the second storagesite and storage controllers at the first storage site may be configuredaccording to a disaster recovery configuration such that when a disasterof the first storage site occurs, the third storage controller and/orthe fourth storage controller may provide client devices with switchoverdata access to the first storage aggregate using mirrored data withinthe remote storage device assigned to the first storage aggregate.

In an example, a disaster of the first storage site may be identified(e.g., a power outage of a building/location comprising the firststorage site, which may not result in a disaster of the second storagesite remotely located in a different building/location). At 308,ownership of the remote storage device may be reassigned from a storagecontroller at the first storage site to a storage controller at thesecond storage site (e.g., the third storage aggregate and/or the fourthstorage aggregate may take ownership of the remote storage device). Thatis, the first storage controller and the second storage controller maybe affected by the disaster of the first storage site, and thus may beunable to provide access to data within the local storage device.However, the third storage controller and/or the fourth storagecontroller, located at the second storage site, may be unaffected by thedisaster, and thus may take ownership of the remote storage device forswitchover operation in order to provide I/O access to the mirrored datawithin the remote storage device. In this way, data access may beprovided to the remote storage device (e.g., by the third storagecontroller and/or the fourth storage controller based upon thereassignment of ownership).

At 310, a gate may be created for the local storage device. In anexample, the gate may be created during the switchover of the remotestorage device to the storage controllers at the second storage site. Inan example of creating the gate, a storage device assignment manager(e.g., a storage area network (SAN) ownership layer configured tofacilitate automated reconstruction and/or automated synchronizationduring disaster recovery) may be instructed to ignore the local storagedevice, such that the local storage device is not exposed to one or morestorage layers that may otherwise perform automated reconstructionand/or automated synchronization.

In an example, the gate blocks automated reconstruction associated withthe local storage device. For example, automated reconstruction may be amechanism that identifies local storage devices having a logicalassociation (e.g., the local storage device and the second local storagedevice may both be assigned to the first storage aggregate and/or mayhave a raid configuration or other backup configuration). If theautomated reconstruction determines that one of the local storagedevices of the logical association is online and another is offline,then the automated reconstruction may reconstruct/rebuild the offlinelocal storage device (e.g., based upon an assumption that the offlinelocal storage device has failed). Thus, if the gate was not created forthe local storage device and the second local storage device is broughtonline before the local storage device (e.g., an administrator may firstpower on the second local storage device during recovery of the firststorage site, and may then proceed to power on the local storage deviceafter the second local storage device has been powered on), then theautomated reconstruction would begin reconstructing the local storagedevice even though the local storage device will be momentarily broughtonline by the administrator after the second local storage device. Inthis way, gates may be created for the local storage device, the secondlocal storage device, and/or other local storage devices so that suchlocal storage devices are concurrently brought online, which maymitigate unnecessary automated reconstruction otherwise occurring due tobringing local storage devices online in a staggered manner.

In another example, the gate blocks automated synchronization of thelocal storage device using the remote storage device. For example,automated synchronization may be a mechanism that automaticallyoverwrites the local storage device with data from the remote storagedevice (e.g., based upon an assumption that the remote storage devicehas relatively more recent data due to the third storage controllerand/or the fourth storage controller using the remote storage device forswitchover operation where new data may be written to the remote storagedevice). However, data within the local storage device may be preferredover data within the remote storage device (e.g., based upon a priordisconnection between the first storage site and the second storage siteresulting in the local storage device comprising data that was nevermirrored to the remote storage device). In this way, gates may becreated for local storage devices so that an administrator mayselectively determine whether to use the local storage device or theremote storage device as a synchronization template.

At 312, access to the local storage device and/or other local storagedevices may be restored. In an example, a user restoration command maybe received for the first storage site, such as for restoration of thefirst storage controller, the second storage controller, and/or thefirst storage aggregate associated with the first storage site. At 314,the gate may be removed from the local storage device. In an example,gates may be concurrently removed from the local storage device and/orother local storage devices, which may mitigate unnecessary automatedreconstruction of local storage devices that may otherwise occur frombringing local storage devices online in a staggered manner. In anexample of removing the gate, a storage device assignment manager may beinstructed to expose the local storage device to one or more storagelayers (e.g., to resume normal access, management, and/or operationassociated with the local storage device).

At 316, synchronization may be facilitated between the local storagedevice and the remote storage device. In an example, responsive to thelocal storage device being designated as the synchronization template,the remote storage device may be synchronized based upon thesynchronization template. Responsive to the remote storage device beingdesignated as the synchronization template, the local storage device maybe synchronized based upon the synchronization template.

In an example, the first storage aggregate at the first storage site maybe restored. Ownership of the remote storage device and/or the localstorage device may be (re)assigned to storage controllers at the firststorage site. In this way, the first storage aggregate may be restoredso that the first storage controller and/or the second storagecontroller may retake ownership of and/or provide data access to thefirst storage aggregate, such as the local storage device. At 318, themethod ends.

FIGS. 4A-4G illustrate examples of a system 401, comprising a gatecomponent 424, for controlling restoration of a storage aggregate. FIG.4A illustrates an example 400 of a first storage site 402 comprising astorage controller (A1) 404 and a storage controller (A2) 406. Thestorage controller (A1) 404 and/or the storage controller (A2) 406 mayprovide data access to a storage aggregate (A) associated with a firstlocal storage device (A) 410, a second local storage device (A) 412, afirst remote storage device (A) 414, and a second remote storage device(A) 416. The first local storage device (A) 410 and the second localstorage device (A) 412 may be located at the first storage site 402. Thefirst remote storage device (A) 414 and the second remote storage device(A) 416 may be located at a second storage site 418. The second storagesite 402 comprises a storage controller (B1) 420 and a storagecontroller (B2) 422 that are configured to provide data access to astorage aggregate (B) associated with a local storage device (B) 424located at the second storage site 418 and a remote storage device (B)426 located at the first storage site 402.

FIG. 4B illustrates an example 430 of identifying a disaster of thefirst storage site 402. In an example, the disaster affects availabilityof the storage controller (A1) 404, the storage controller (A2) 406,and/or access through the first storage site 402 to the first localstorage device (A) 410, the second local storage device (A) 412, and/orthe remote storage device (B) 426.

FIG. 4C illustrates an example 440 of the storage controller (B1) 420and/or the storage controller (B2) 422 taking ownership of the firstremote storage device (A) 414 and/or the second remote storage device(A) 416. For example, ownership of the first remote storage device (A)414 is reassigned to the storage controller (B1) 420 resulting in thefirst remote storage device (A) 414 b. Ownership of the second remotestorage device (A) 416 is reassigned to the storage controller (B2) 422resulting in the second remote storage device (A) 416 b. In this way,the storage controller (B1) 420 and/or the storage controller (B2) 422may provide switchover disaster recovery for the storage controller (A1)404 and storage controller (A2) 406 by providing I/O access to datamirrored from the first local storage device (A) 410 to the first remotestorage device (A) 414 b and providing I/O access to data mirrored fromthe second local storage device (A) 412 to the second remote storagedevice (A) 416 b.

In an example, the gate component 424 is configured to create a firstgate 442 for the first local storage device (A) 410 and/or a second gate444 for the second local storage device (A) 412. In another example, asingle gate is created for the first local storage device (A) 410 andthe second local storage device (A) 412. In an example, the gatecomponent 424 may create the first gate 442 and/or the second gate 444by instructing a storage device assignment manager 446 to ignore thefirst local storage device (A) 410 and/or the second local storagedevice (A) 412. In an example, the first gate 442 and/or the second gate444 are configured to block automated reconstruction associated with thefirst local storage device (A) 410 and/or the second local storagedevice (A) 412. Blocking automated reconstruction may mitigateunnecessary reconstruction/recreation of local storage devices. Forexample, the second gate 444 may block automated reconstruction of thesecond local storage device (A) 412 that may otherwise occur when thefirst local storage device (A) 410 is brought online before the secondlocal storage device (A) 412 is brought online (e.g., without the secondgate 444, the automated reconstruction may start unnecessarilyreconstructing the second local storage device (A) 412 after determiningthat the first local storage device (A) 410 is online and that thesecond local storage device (A) 412 is offline). In another example, thefirst gate 442 and/or the second gate 444 are configured to blockautomated synchronization between local storage devices and remotestorage devices. For example, an administrator may prefer data within alocal storage device over data within a remote storage device, and thusa gate may block automated synchronization that may otherwiseautomatically overwrite the local storage device with the data from theremote storage device.

FIG. 4D illustrates an example 450 of restoring the first local storagedevice (A) 410 and/or the second local storage device (A) 412. The firstgate 442 and/or the second gate 444 may block the automatedreconstruction and/or the automated synchronization that may otherwiseoccur for the first local storage device (A) 410 and/or the second localstorage device (A) 412 during and/or after the restoration.

A user restoration command may be received. For example, the userrestoration command may be received from an administrator that hasbrought the first local storage device (A) 410 and the second localstorage device (A) 412 at the first storage site 402 online. FIG. 4Eillustrates an example 460 of the gate component 424 concurrentlyremoving the first gate 442 and the second gate 444 based upon the userrestoration command. In an example, the gate component 424 may removethe first gate 442 and/or the second gate 444 by instructing the storagedevice assignment manager 446 to expose the first local storage device(A) 410 and/or the second local storage device (A) 412 to one or morestorage layers. In this way, the first local storage device (A) 410 andthe second local storage device (A) 412 are currently brought online,which may mitigate unnecessary automated reconstruction that mayotherwise occur if the first local storage device (A) 410 and the secondlocal storage device (A) 412 were brought online in a staggered manner.

The storage controller (B1) 420 and/or the storage controller (B2) 422acquire ownership of the first local storage device (A) 410 and/or thesecond local storage device (A) 412. Ownership of the first localstorage device (A) 410 is reassigned to the storage controller (B1) 420resulting in a first local storage device (A) 410 b. Ownership of thesecond local storage device (A) 412 is reassigned to the storagecontroller (B2) 422 resulting in a second local storage device (A) 412b. Synchronization is facilitated (e.g., by the storage controller (B1)420 and/or the storage controller (B2) 442) between the first localstorage device (A) 410 b and the first remote storage device (A) 414 band/or between the second local storage device (A) 412 b and the secondremote storage device (A) 416 b. In an example, the first local storagedevice (A) 410 b is overwritten with data from the first remote storagedevice (A) 414 b. In another example, the first remote storage device(A) 414 b is overwritten with data from the first local storage device(A) 410 b. In an example, the second local storage device (A) 412 b isoverwritten with data from the second remote storage device (A) 416 b.In another example, the second remote storage device (A) 416 b isoverwritten with data from the second local storage device (A) 412 b.

FIG. 4F illustrates an example 480 of restoring the storage controller(A1) 404 and the storage controller (A2) 406 at the first storage site402. FIG. 4G illustrates an example 490 of reassigning the one or morestorage devices from the second storage site 418 to the first storagesite 402. For example, ownership of the first local storage device 410 bis reassigned to the storage controller (A1) 404 resulting in a firstlocal storage device 410 a. Ownership of the second local storage device412 b is reassigned to the storage controller (A2) 406 resulting in asecond local storage device 412 a. Ownership of the first remote storagedevice 414 b is reassigned to the storage controller (A1) 404 resultingin a first remote storage device 414 a. Ownership of the second remotestorage device 416 b is reassigned to the storage controller (A2) 406resulting in a second remote storage device 416 a. In this way, thestorage controller (A1) 404 and/or the storage controller (A2) 406 ofthe first storage site 402 may take ownership of and/or provide I/Oaccess to the first local storage device (A) 410 a, the second localstorage device (A) 412 a, the first remote storage device (A) 414 a, thesecond remote storage device (A) 416 a and/or other storage devices.

Still another embodiment involves a computer-readable medium comprisingprocessor-executable instructions configured to implement one or more ofthe techniques presented herein. An example embodiment of acomputer-readable medium or a computer-readable device that is devisedin these ways is illustrated in FIG. 5, wherein the implementation 500comprises a computer-readable medium 508, such as a CD-R, DVD-R, flashdrive, a platter of a hard disk drive, etc., on which is encodedcomputer-readable data 506. This computer-readable data 506, such asbinary data comprising at least one of a zero or a one, in turncomprises a set of computer instructions 504 configured to operateaccording to one or more of the principles set forth herein. In someembodiments, the processor-executable computer instructions 504 areconfigured to perform a method 502, such as at least some of theexemplary method 300 of FIG. 3, for example. In some embodiments, theprocessor-executable instructions 504 are configured to implement asystem, such as at least some of the exemplary system 401 of FIGS.4A-4G, for example. Many such computer-readable media are contemplatedto operate in accordance with the techniques presented herein.

It will be appreciated that processes, architectures and/or proceduresdescribed herein can be implemented in hardware, firmware and/orsoftware. It will also be appreciated that the provisions set forthherein may apply to any type of special-purpose computer (e.g., filehost, storage server and/or storage serving appliance) and/orgeneral-purpose computer, including a standalone computer or portionthereof, embodied as or including a storage system. Moreover, theteachings herein can be configured to a variety of storage systemarchitectures including, but not limited to, a network-attached storageenvironment and/or a storage area network and disk assembly directlyattached to a client or host computer. Storage system should thereforebe taken broadly to include such arrangements in addition to anysubsystems configured to perform a storage function and associated withother equipment or systems.

In some embodiments, methods described and/or illustrated in thisdisclosure may be realized in whole or in part on computer-readablemedia. Computer readable media can include processor-executableinstructions configured to implement one or more of the methodspresented herein, and may include any mechanism for storing this datathat can be thereafter read by a computer system. Examples of computerreadable media include (hard) drives (e.g., accessible via networkattached storage (NAS)), Storage Area Networks (SAN), volatile andnon-volatile memory, such as read-only memory (ROM), random-accessmemory (RAM), EEPROM and/or flash memory, CD-ROMs, CD-Rs, CD-RWs, DVDs,cassettes, magnetic tape, magnetic disk storage, optical or non-opticaldata storage devices and/or any other medium which can be used to storedata.

Although the subject matter has been described in language specific tostructural features or methodological acts, it is to be understood thatthe subject matter defined in the appended claims is not necessarilylimited to the specific features or acts described above. Rather, thespecific features and acts described above are disclosed as exampleforms of implementing at least some of the claims.

Various operations of embodiments are provided herein. The order inwhich some or all of the operations are described should not beconstrued to imply that these operations are necessarily orderdependent. Alternative ordering will be appreciated given the benefit ofthis description. Further, it will be understood that not all operationsare necessarily present in each embodiment provided herein. Also, itwill be understood that not all operations are necessary in someembodiments.

Furthermore, the claimed subject matter is implemented as a method,apparatus, or article of manufacture using standard programming orengineering techniques to produce software, firmware, hardware, or anycombination thereof to control a computer to implement the disclosedsubject matter. The term “article of manufacture” as used herein isintended to encompass a computer program accessible from anycomputer-readable device, carrier, or media. Of course, manymodifications may be made to this configuration without departing fromthe scope or spirit of the claimed subject matter.

As used in this application, the terms “component”, “module,” “system”,“interface”, and the like are generally intended to refer to acomputer-related entity, either hardware, a combination of hardware andsoftware, software, or software in execution. For example, a componentincludes a process running on a processor, a processor, an object, anexecutable, a thread of execution, a program, or a computer. By way ofillustration, both an application running on a controller and thecontroller can be a component. One or more components residing within aprocess or thread of execution and a component may be localized on onecomputer or distributed between two or more computers.

Moreover, “exemplary” is used herein to mean serving as an example,instance, illustration, etc., and not necessarily as advantageous. Asused in this application, “or” is intended to mean an inclusive “or”rather than an exclusive “or”. In addition, “a” and “an” as used in thisapplication are generally be construed to mean “one or more” unlessspecified otherwise or clear from context to be directed to a singularform. Also, at least one of A and B and/or the like generally means A orB and/or both A and B. Furthermore, to the extent that “includes”,“having”, “has”, “with”, or variants thereof are used, such terms areintended to be inclusive in a manner similar to the term “comprising”.

Many modifications may be made to the instant disclosure withoutdeparting from the scope or spirit of the claimed subject matter. Unlessspecified otherwise, “first,” “second,” or the like are not intended toimply a temporal aspect, a spatial aspect, an ordering, etc. Rather,such terms are merely used as identifiers, names, etc. for features,elements, items, etc. For example, a first set of information and asecond set of information generally correspond to set of information Aand set of information B or two different or two identical sets ofinformation or the same set of information.

Also, although the disclosure has been shown and described with respectto one or more implementations, equivalent alterations and modificationswill occur to others skilled in the art based upon a reading andunderstanding of this specification and the annexed drawings. Thedisclosure includes all such modifications and alterations and islimited only by the scope of the following claims. In particular regardto the various functions performed by the above described components(e.g., elements, resources, etc.), the terms used to describe suchcomponents are intended to correspond, unless otherwise indicated, toany component which performs the specified function of the describedcomponent (e.g., that is functionally equivalent), even though notstructurally equivalent to the disclosed structure. In addition, while aparticular feature of the disclosure may have been disclosed withrespect to only one of several implementations, such feature may becombined with one or more other features of the other implementations asmay be desired and advantageous for any given or particular application.

What is claimed is:
 1. A method, comprising: assigning ownership of afirst storage device from a first node to a second node based upon afailure of the first node; creating a gate for the first storage deviceto block automated synchronization between the first storage device anda second storage device associated with the second node; and providingaccess to the first storage device through the second node.
 2. Themethod of claim 1, comprising: removing the gate from the first storagedevice based upon a restoration command.
 3. The method of claim 2,comprising: synchronizing the first storage device and the secondstorage device based upon the restoration command.
 4. The method ofclaim 1, comprising: utilizing the gate to instruct a storage deviceassignment manager to ignore the first storage device.
 5. The method ofclaim 2, wherein the removing the gate comprises: instructing a storagedevice assignment manager to expose the first storage device to astorage layer.
 6. The method of claim 5, comprising: sending aninstruction to ignore the first storage device to a storage area network(SAN) assignment layer comprising the storage device assignment manager.7. The method of claim 1, comprising: providing access to the secondstorage device through the second node.
 8. The method of claim 1,comprising: reassigning the first storage device from the second node tothe first node based upon the first node recovering.
 9. A non-transitorymachine readable medium comprising instructions for performing a method,which when executed by a machine, causes the machine to: assignownership of a first storage device from a first node to a second nodebased upon a failure of the first node; create a gate for the firststorage device to block automated synchronization between the firststorage device and a second storage device associated with the secondnode; and provide access to the first storage device through the secondnode.
 10. The non-transitory machine readable medium of claim 9, whereinthe instructions cause the machine to: remove the gate from the firststorage device based upon a restoration command.
 11. The non-transitorymachine readable medium of claim 10, wherein the instructions cause themachine to: synchronize the first storage device and the second storagedevice based upon the restoration command.
 12. The non-transitorymachine readable medium of claim 9, wherein the instructions cause themachine to: utilize the gate to instruct a storage device assignmentmanager to ignore the first storage device.
 13. The non-transitorymachine readable medium of claim 10, wherein the instructions cause themachine to: instruct a storage device assignment manager to expose thefirst storage device to a storage layer.
 14. The non-transitory machinereadable medium of claim 13, wherein the instructions cause the machineto: send an instruction to ignore the first storage device to a storagearea network (SAN) assignment layer comprising the storage deviceassignment manager.
 15. The non-transitory machine readable medium ofclaim 9, wherein the instructions cause the machine to: provide accessto the second storage device through the second node.
 16. Thenon-transitory machine readable medium of claim 9, wherein theinstructions cause the machine to: reassign the first storage devicefrom the second node to the first node based upon the first noderecovering.
 17. A computing device comprising: a memory comprisingmachine executable code; and a processor coupled to the memory, theprocessor configured to execute the machine executable code to cause theprocessor to: assign ownership of a first storage device from a firstnode to a second node based upon a failure of the first node; create agate for the first storage device to block automated synchronizationbetween the first storage device and a second storage device associatedwith the second node; and provide access to the first storage devicethrough the second node.
 18. The computing device of claim 17, whereinthe machine executable code causes the processor to: remove the gatefrom the first storage device based upon a restoration command.
 19. Thecomputing device of claim 18, wherein the machine executable code causesthe processor to: synchronize the first storage device and the secondstorage device based upon the restoration command.
 20. The computingdevice of claim 17, wherein the machine executable code causes theprocessor to: utilize the gate to instruct a storage device assignmentmanager to ignore the first storage device.